Field of the Invention
The invention relates in general to a display device, and more particularly to a control circuit and associated control method applied to Digital Visual Interface (DVI).
Description of the Related Art
Conventionally, when a Digital Visual Interface (DVI) connector of a display device connects to a display card of an image transmitter (e.g., a computer host) through a connecting cable, the display card directly reads extended display identification data (EDID) stored in the display device, and transmits display data according to the EDID to the display device. The selection of the EDID is set using an on-screen display (OSD) by a user. When the user sets the display device to be in a Digital Visual Interface-Analog (DVI-A) (or referred to as Video Graphics Array (VGA)) mode, the display card has access to only the EDID of DVI-A. Similarly, when the user sets the display device to be in a Digital Visual Interface-Digital (DVI-D) mode, the display card has access to only the EDID of DVI-D.
As previously described, the EDID that the display card reads is determined according to the user setting, and so it is probable that the display card receives incorrect EDID that may lead to subsequent display errors and operation complications. For example, assume that the display card transmits digital signals and is connected to the display device through a DVI-D connecting cable, and the setting of the display device is the DVI-A mode. At this point, the display card reads the EDID of DVI-A, and determines that the DVI-A is not supported. Thus, the display card does not transmit any display data to the display device. Further, there is no use if the user again sets the display device to the DVI-D mode, as the display card does not again read the EDID stored in the display device. In the above situation, the user can only again set the display device to the DVI-D mode and unplug and re-plug the connecting cable, and the display device is then able to display normally.
On the other hand, assume that the display card transmits analog signals, the connecting cable is a DVI-A (or VGA) connecting cable, and the display device is set to the DVI-D mode. At this point, the display card reads the EDID of DVI-D, and transmits display data with incorrect timing to the display device. In the above situation, the user can only again set the display device to the DVI-A mode and unplug and re-plug the connecting cable, so as to be able to view a correct display image.